The present invention relates generally to capacitors and in particular the present invention relates to multi-layer integrated circuit capacitors.
Integrated circuit devices operate using one or more power supplies. These power supplies traditionally have sufficient voltage and power to supply numerous circuits without interruption. Power supplies, however, have been decreasing in size. This forces the integrated circuit manufactures to decrease operating voltages and power requirements.
Under normal circumstances a power supply will be able to provide sufficient power to all circuits coupled to the supply. However, voltage drops on power supply lines can occur when there is a sudden increase in demand for power. This lower voltage can reduce switching times of the transistors in a circuit coupled to the supply. This in turn can cause a loss in performance of the circuit.
Decoupling capacitors can be provided in a circuit that is coupled to the power supply to minimize this voltage drop. That is, a decoupling capacitor stores a charge that helps stabilize changes in the voltage supply line. The response of these decoupling capacitors depends on the inductance and resistance of the capacitor and the amount of capacitance available. Fabricating decoupling capacitors in the same integrated circuit provides difficulty in obtaining sufficient capacitance for reliable decoupling.
An alternate approach is to provide numerous discrete capacitors external to a circuit package. These discrete capacitors are typically attached in parallel to a package, or circuit board. Physical space must be left between the capacitors for placement handling and soldering to the package. The spacing requires longer interconnect lines that results in higher inductance/resistance and less capacitance due to the wasted space and the terminal spacing on the capacitors. In addition the capacitors have edge, terminations that have higher inductance and resistance.
For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for a decoupling capacitor that has more capacitance while controlling resistance and inductance characteristics.